1. Field of the Invention
The present invention relates to a plant for the treatment of products, of the type which includes an apparatus for treating said products, the apparatus being combined with a conveyor for introducing the products into the apparatus and for extracting said products from said apparatus, the plant furthermore including means for detecting the products treated by said apparatus, these means being suitable for determining a value representative of the quality and/or the quantity of products treated by said apparatus.
The invention relates in particular to plants for the treatment of food products, for example cooking plants, or else to the deep-freezing of food products, such as portions of ground meat or fish fillets, prepared dishes, dairy products, or else Viennese breads and buns. It will be understood that the list given above cannot be regarded as exhaustive, but is in fact purely illustrative of the many possibilities in the food industry.
2. Description of the Related Art
Known deep-freezing plants include, for example, a deep-freezing tunnel right through which a belt conveyor passes, the products to be frozen being deposited on said belt conveyor. The belt conveyor circulates continuously through the deep-freezing tunnel.
The deep-freezing tunnel is supplied with a cryogenic fluid, such as liquid nitrogen or liquid carbon dioxide. This cryogenic fluid is brought into contact with the products to be treated. On contact with the products, the cryogenic fluid vaporizes, thus refrigerating the products.
It is known to place, upstream of the deep-freezing tunnels, means for detecting the products introduced into the tunnel. These means are used, for example, to determine the number of products or the mass of products treated by the tunnel. They conventionally include balances allowing the weight of the products introduced into the deep-freezing tunnel to be determined continuously.
These balances generally include a belt conveyor located upstream of the belt conveyor of the deep-freezing tunnel. Weighing devices are placed beneath the conveyor so as to continuously determine the weight of the products traveling on the conveyor. If several products, for example portions of ground meat, are placed side by side along the width of the conveyor, several weighing devices are placed side by side in the paths along which the products move.
The weighing devices used in the known detection means currently include moving parts and employ a sophisticated weighing mechanism. This mechanism is sensitive to the influence of the temperature. In particular, the weighing devices are subject to blockages due to the frost when they are used at a very low temperature.
Under these conditions, the known balances must be placed away from the deep-freezing tunnel so as to avoid malfunctions resulting from the low temperatures.
In addition, the weighing devices cannot be directly associated with the conveyor of the deep-freezing tunnel.
Consequently, it is necessary to provide means for transferring the products from the conveyor specific to the balances to the conveyor specific to the deep-freezing tunnel. The use of such transfer means causes degradation of the products during their transfer.
Again by way of illustration of the examples of applications in which it is advantageous to be able to determine the mass, size or surface area of the products entering such tunnels or apparatuses for the treatment of food products, mention may be made of the case of machine [sic] for packaging food products under packaging which traps an atmosphere containing ozone.
Thus, the following may be used, for example:
N.sub.2 /CO.sub.2 /O.sub.2 /O.sub.3 atmospheres, for example for meat products or fish products. By way of illustration, atmospheres containing 1000 to 15,000 ppm/weight of ozone, which include a few percent to a few tens of percent of oxygen and a few tens of percent of CO.sub.2, will typically be used here, depending on the intended product; PA1 N.sub.2 /O.sub.2 /O.sub.3 atmospheres, for example for vegetables (even if in some cases it may happen that, in the case of vegetables, the atmosphere includes a little CO.sub.2), such atmospheres typically containing up to 1500 ppm/weight of ozone, depending on the intended product. PA1 the line of sight of said camera extends so as to be approximately perpendicular to the plane of movement of said conveyor; PA1 said data processing unit includes means for triggering the taking of an image at predefined triggering times and said image processing means include means capable of computing a value representative of the density of products on the conveyor at each triggering time from said digital image of said section of the conveyor at that time; PA1 said camera is a camera of the monochrome or color type; PA1 said camera is a camera of the color type and said image processing comprises an analysis of the colors present in the image, allowing, by comparison with a reference color, said value representative of the density of products on the conveyor to be determined; PA1 the plant includes means for placing the products on said conveyor in a predetermined pattern, reproduced sequentially along said conveyor with a variable quantity of products for each pattern, and it includes, connected to said data processing unit, means for counting the number of patterns traveling past the camera, and said data processing unit includes means for evaluating the value representative of the quantity of products treated from said value representative of the density of products on the conveyor, this being computed at each triggering time, and from the number of patterns counted; PA1 said counting means include an optical barrier connected to said data processing unit and placed transversely to the conveyor, the beam of said barrier lying in the plane of movement of the products so as to be interrupted by the products traveling on the conveyor; PA1 the optical barrier includes, near the conveyor, an end for the emission of the beam and an end for the reception of the beam, and these two ends are associated with nozzles for ejecting a gas for protecting said ends, especially a hot gas; PA1 according to another embodiment of the counting means, these include, near the conveyor, an ultrasonic or microwave barrier connected to said data processing unit and placed transversely to the conveyor, the beam of said barrier lying in the plane of movement of the products (P) so as to be interrupted by the products (P) traveling on the conveyor; PA1 said camera is a camera of the infrared type and said image processing makes it possible to obtain, apart from a value representative of the density of products on the conveyor (as in the case of the other camera types mentioned), a value representative of the temperature of the products on the conveyor; PA1 said image processing means include means for differentiating, in said image, those areas of the conveyor that are covered by a product from those areas of the conveyor that are left free, as well as means for analyzing said differentiated areas in said image in order to determine a value representative of the quantity of products treated; PA1 said means for analyzing said differentiated areas include means for producing, over the entire extent of the image, a first histogram representative of the number of pixels corresponding to those areas of the conveyor that are covered by a product, for each line of the image in the direction of movement of the conveyor, means for producing, over the entire extent of the image, a second histogram representative of the number of pixels corresponding to those areas of the conveyor that are covered by a product, for each line of the image in the direction perpendicular to the direction of movement of the conveyor, and means for comparing the values of the peaks of the first and second histograms thus produced with first and second threshold values for determining the density of products treated; PA1 said treatment apparatus is an apparatus for cooling food products by bringing the products into contact with a cryogenic fluid and it includes, connected to said data processing unit, means for measuring the quantity of cryogenic fluid with which the products are brought into contact, and said data processing unit includes means for computing the temperature of each product leaving said apparatus depending on the value representative of the quantity of products treated and on the measured quantity of cryogenic fluid; and PA1 said data processing unit includes means for storing the curve of the variation in enthalpy of a product as a function of its temperature, and means for determining the exit temperature of a product from said enthalpy curve, from the measured quantity of cryogenic fluid, from the value representative of the quantity of products treated and from the initial temperature of the products.
However, it has moreover been clearly demonstrated that ozone reacts more depending on the area of the product in question than, for example, depending on its mass or its volume. It will therefore be understood that it is very advantageous to determine the surface area of the entering products correctly, so that, for example, the quantity of ozone produced by the ozonizer is subject to feedback control so as to efficiently adapt to this area, for example according to a pre-established calibration curve.